Pressure devices, for example, also such subject to the “Guideline 97/23/EH of the European Parliament and the Advisory of 29 May 1997 for equalizing the laws and regulations of the member states concerning pressure devices” or corresponding national laws and regulations—, at times, also referred to as pressure device guidelines—, such as, for instance, the “Fourteenth enactment of the product safety law” (14. ProdSV) or the “ASME Boiler and Pressure Vessel Code” (ASME U-Stamp), find varied application in industrial settings, not least of all also in industrial measuring- and automation technology, for example, in the form of tanks for liquefied gas, autoclaves or other containers for accommodating, respectively storing, fluids under increased pressure relative to the surrounding atmosphere, in the form of pipelines suitable for the transport of such fluids under increased pressure or also in the form of plants formed by means of such containers and/or pipelines, consequently such regularly operated with increased operational pressures. To be mentioned as other representatives of such pressure devices are additionally measuring transducers communicating with the aforementioned pipelines, respectively containers, consequently contacted by fluid guided therein, respectively also flowed through by the fluid, for generating a measurement signal corresponding to a measured variable to be registered for the fluid, respectively measuring systems formed by means of such measuring transducers and transmitter electronics electrically connected therewith, such as e.g. Coriolis, mass flow, measuring device, vortex, flow measuring devices or also ultrasonic, flow measuring devices or measuring apparatuses formed therewith, not least of all also such, in the case of which the lumen of the pressure device is formed by means of a tube arrangement having at least one measuring tube conveying fluid during operation. Examples of such pressure devices, regularly also being subject to one or more the aforementioned laws or regulations and/or embodied as measuring systems for fluids standing at least, at times, under high pressure of over 50 bar, are described, among other things, in European Patents, EP A 816 807, EP A 919 793, and EP A 1 001 254, US A 2001/0029790, US A 2004/0261541, US A 2005/0039547, US A 2006/0266129, US A 2007/0095153, US A 2007/0234824, US A 2008/0141789, US A 2011/0113896, US A 2011/0161018, US A 2011/0219872, US A 2012/0123705, U.S. Pat. No. 4,680,974, and Published International Applications WO A 2005/050145, WO A 2009/134268, WO A 90/15310, WO A 95/16897, WO A 96/05484, WO A 97/40348, WO A 98/07009 or WO A 99/39164.
The measuring systems disclosed therein are each formed by means of a measuring transducer of vibration-type insertable into the course of a pipeline and flowed-through by fluid during operation, wherein each of the measuring transducers comprises a tube arrangement formed by means of at least one, essentially straight or at least sectionally curved, e.g. U-, or V-shaped, measuring tube, in such a manner that wall and lumen are also, in each case, formed by means of the at least one measuring tube and the lumen communicates during operation with a lumen of the connected pipeline.
In operation of the pressure device, respectively the measuring system formed therewith, the at least one measuring tube is actively excited to execute mechanical oscillations for the purpose of generating oscillation signals influenced by the through flowing fluid, for example, by its mass flow rate, its density and/or its viscosity, and serving, in each case, also as measurement signal of the measuring transducer. Other examples of such measuring systems formed by means of a pressure device are described, among other things, also in U.S. Pat. Nos. 5,796,011, 7,284,449, 7,017,424, 6,910,366, 6,840,109, 5,576,500, 6,651,513, US A 2005/0072238, US A 2006/0225493, US A 2008/0072688, US A 2011/0265580, and Published International Applications, WO A 2004/023081, WO A 2006/009548, WO A 2008/042290, WO A 2007/040468 or WO A 2013/060659.
Each of the measuring transducer includes additionally a measuring transducer housing surrounding the tube arrangement, namely a measuring transducer housing forming a cavity accommodating the tube arrangement as well as, formed on the measuring transducer housing, respectively integrated therein, an inlet-side connecting flange as well as an outlet-side connecting flange for connecting the tube arrangement with the pipeline. For the case, in which the tube arrangement, consequently the lumen, is formed by means of two or more measuring tubes, the measuring tubes are most often inserted into the pipeline to form flow paths for parallel flow via a flow divider extending on the inlet side between the measuring tubes and the inlet-side connecting flange as well as via a flow divider extending on the outlet side between the measuring tubes and the outlet-side connecting flange. The measuring transducer housing serves besides for holding the tube arrangement placed within the cavity formed by the measuring transducer housing, especially, also to protect such as well as other internally lying components, for example, a sensor arrangement of the measuring transducer, against external, environmental influences, such as e.g. dust or water spray, consequently to provide a cavity as hermetically sealed as possible. Particularly in the case of pressure devices of the type being discussed, the user can, moreover, at times, also require of the measuring transducer housing that it in the case of an unsealed or bursting tube arrangement can withstand the static internal pressure within the cavity lying most often significantly over the atmospheric, external pressure at least for a predetermined time leak-free. Consequently, the measuring transducer housing must have a certain pressure resistance; compare, for this, also the above mentioned US A 2006/0266129, US A 2005/0039547, US A 2001/0029790, Published International Application WO A 90/15310, EPA 1 001 254, respectively the international patent application PCT/EP2012/070924. Particularly for applications with toxic or easily flammable fluids, the measuring transducer housing must, in such case, at times, also be able to fulfill the requirements placed on safety containers.
Measuring systems of the type being discussed, consequently pressure devices formed therewith, are additionally usually connected with one another and/or with corresponding electronic controllers by means of a—wired and/or radio-based—data transmission network provided within the superordinated data processing system, for example, programmable logic controllers (PLC) installed on-site or with stationary process-control computers in a remote control room, where the measured values produced by means of the measuring system and digitized and correspondingly encoded in suitable manner are forwarded. By means of process-control computers, using correspondingly installed software components, the transmitted measured values can be further processed and visualized as corresponding measurement results e.g. on monitors and/or converted into control signals for other field devices embodied as actuating devices, such as e.g. magnetic valves, electric motors, etc. Accordingly, the data processing system serves usually also to condition the measured value signal delivered from the transmitter electronics in a manner corresponding to the requirements of downstream data transmission networks, for example, suitably to digitize the measured value signal and, in given cases, to convert it into a corresponding telegram, and/or to evaluate it on-site. For such purpose, there are provided in such data processing systems, electrically coupled with the respective connecting lines, evaluating circuits, which pre- and/or further process as well as, in case required, suitably convert, the measured values received from the respective transmitter electronics. Serving for data transmission in such industrial data processing systems, at least sectionally, are fieldbusses, especially serial fieldbusses, such as e.g. FOUNDATION FIELDBUS, CAN, CAN-OPEN RACKBUS-RS 485, PROFIBUS, etc., or, for example, also networks based on the ETHERNET-standards as well as the corresponding, most often application independent, standardized transmission-protocols.
Pressure devices of the type being discussed can during operation be exposed, at times, to increased loadings, in given cases, also loadings above earlier agreed limit values, consequently loadings damaging to the integrity of the pressure device, be it through undesired overloadings as regards the operating pressure, through the occurrence of undesired inhomogeneities in a fluid having, in given cases, also high flow velocities of greater than 10 ms−1, for example, in the form of solid particles entrained in the flowing fluid and/or gas bubbles entrained in liquid carrier medium, and/or undesired thermal overloading, for example, as a result of too high temperatures of the respective fluid and/or unfavorable time temperature curves, along with spatial temperature distributions unfavorable to the integrity of the pressure device. As a result of such loadings, respectively overloadings, the wall of the pressure device can be partially so damaged—, for instance, as a result of plastic deformation of the wall and/or as a result of wear of the wall, namely as a result of removal of material from the surface facing the lumen —, that the pressure device has a pressure resistance lessened in comparison to an original, respectively nominal, pressure resistance; this, for example, also in such a manner that damage of the wall within a very short time can exceed a critical damage earlier set for the respective pressure device. The critical damage of the wall can, for example, correspond to a damage specifically ascertained for the respective type, respectively the particular series of the pressure device, damage which, in given cases, also requires immediate inspection of the respective pressure device, and/or which corresponds to lessened remaining life of the particular pressure device requiring an immediate, respectively extraordinary, replacement of the pressure device.
For the mentioned case, in which the pressure device is a measuring transducer, respectively a component of a measuring system, the critical damage set for the respective pressure device can also correspond to a lessened accuracy of measurement of the measuring system resulting from such damage, respectively to a, in given cases, no longer tolerable, increased systematic measuring error in the case of generating the measurement signal, for example, as a result of damage to the respective at least one measuring tube. Of special interest, in such case, are also such measuring systems, in the case of which, such as already mentioned, the pressure device is formed by means of a measuring transducer of vibration-type. On the one hand, their respective measuring tubes are most often embodied as thin walled as possible, in order to achieve an as high as possible sensitivity of their oscillation signals, especially as regards the mass flow rate, respectively density, of the respective fluid to be measured. Consequently, the tube arrangement of such a measuring transducer has usually walls with a comparatively small, namely only low, respectively minimal, allowable safety reserves as regards wall thicknesses providing the pressure resistance. On the other hand, of interest, however, can also be even small damage to the wall, namely damage not yet sinking the pressure resistance of the tube arrangement, respectively of the pressure device formed therewith, to an unallowable low measure, because, such as, among other things, also discussed in the above mentioned EP-A 816 807, WO-A 2005/050145, WO-A 99/39164, WO-A 96/05484, US-A 2007/0095153, respectively US-A 2012/0123705, also such damage, arising distributed most often also spatially rather non-uniformly over the tube arrangement can have considerable effects on the accuracy of measurement of the measuring system, not least of all also those measuring systems with which the mass flow rate, respectively the density, are measured.
Methods, respectively measuring systems with measuring apparatuses, which are suitable, as early as possible, to detect, respectively to be able to predict, undesirably, respectively unallowably high, damage of the aforementioned type to such pressure devices formed by means of measuring transducers of vibration-type, respectively to be able to estimate quantitatively an extent such damage, are described, among other things, in the above mentioned US A 2007/0095153, US A 2006/0266129; European Patent; EP A 816 807, US A 2012/0123705, and Published International Applications, WO A 2005/050145, WO A 96/05484 or WO A 99/39164. Fundamentally, the therein disclosed methods operate based on the evaluation of oscillation signals delivered by means of the measuring transducers during operation, in given cases, also by additional taking into consideration of exciter signals effecting the respective oscillations of the at least one measuring tube. Although these methods, respectively measuring arrangements, in the case of measuring systems, respectively pressure devices, formed by means of measuring transducers of vibration-type can be used very advantageously, respectively applied also in increasing measure, a disadvantage of such methods, respectively measuring arrangements, is to be seen in the fact that they operate based on measurement signals—here the oscillation signals specific for such measuring systems and, thus, are applicable exclusively for such measuring systems, consequently actually only for a relatively small part of the totality of pressure devices. Additionally, the mentioned methods, respectively measuring arrangements, can, at times, also have certain cross sensitivities to measured variables, not least of all to the above referenced measured variables, mass flow rate, density and/or viscosity, representing other than the actual damage, and these cross sensitivities must be correspondingly compensated, be it by applying in the measuring system supplementally provided sensor systems and/or from measured values supplementally ascertained externally of the measuring system, in order reliably to ascertain alarmable damage of the wall, respectively to be able safely to prevent false alarms.